Active horizontal stabilizer for high speed rotorcraft

Abstract

A rotorcraft has a horizontal stabilizer movable about an axis of rotation and a horizontal stabilizer control system configured to control the horizontal stabilizer to at least one of move the rotorcraft into a minimum drag position, maintain the aircraft in a minimum drag position, efficiently achieve a maneuver, enter efficient autorotation, and maintain efficient autorotation.

What is claimed is: 
     
       1. A rotorcraft, comprising:
 a main rotor system; 
 a tail boom; 
 a tail rotor carried by the tail boom; 
 a horizontal stabilizer carried by the tail boom, the horizontal stabilizer comprising a leading edge and the leading edge being movable about an axis of rotation relative to the tail boom; and 
 a horizontal stabilizer control system configured to, in response to the rotorcraft entering autorotation, control the horizontal stabilizer to automatically and without pilot input maximize airflow to the main rotor without requiring a change in pitch of the main rotor system and without prioritizing maintaining a constant longitudinal attitude of the rotorcraft. 
 
     
     
       2. The rotorcraft of  claim 1 , wherein the horizontal stabilizer control system is configured to recognize forward flight of the rotorcraft. 
     
     
       3. The rotorcraft of  claim 2 , wherein the horizontal stabilizer control system is configured to query a lookup table for a predetermined horizontal stabilizer position for a minimum drag position of the rotorcraft. 
     
     
       4. The rotorcraft of  claim 3 , wherein the horizontal stabilizer control system is configured to control a horizontal stabilizer actuator to achieve the predetermined horizontal stabilizer position. 
     
     
       5. The rotorcraft of  claim 4 , wherein the horizontal stabilizer control system is configured to receive information indicative of an actual or predicted instability or disturbance of the rotorcraft from the minimum drag position. 
     
     
       6. The rotorcraft of  claim 5 , wherein the horizontal stabilizer control system is configured to query a lookup table for a predetermined horizontal stabilizer position for counteracting the actual or predicted deviation of the rotorcraft from the minimum drag position. 
     
     
       7. The rotorcraft of  claim 6 , wherein the horizontal stabilizer control system is configured to control a horizontal stabilizer actuator to deviate from the predetermined horizontal stabilizer position associated with the minimum drag position to counteract or prevent the actual or predicted deviation of the rotorcraft from the minimum drag position, respectively. 
     
     
       8. The rotorcraft of  claim 1 , wherein the horizontal stabilizer control system is configured to control a horizontal stabilizer to provide a minimum drag position of the rotorcraft. 
     
     
       9. The rotorcraft of  claim 8 , wherein the horizontal stabilizer control system is configured to temporarily base control of the horizontal stabilizer position on supporting efficient maneuvering rather than minimum drag. 
     
     
       10. The rotorcraft of  claim 9 , wherein the horizontal stabilizer control system is configured to return control of the horizontal stabilizer position to support a minimum drag position of the rotorcraft instead of efficient maneuvering of the rotorcraft. 
     
     
       11. The rotor craft of  claim 10 , wherein the horizontal stabilizer control system is configured to recognize a return to substantially level fast forward flight. 
     
     
       12. The rotorcraft of  claim 11 , wherein the horizontal stabilizer control system is configured to resume controlling the horizontal stabilizer position to achieve a minimum drag position of the rotorcraft. 
     
     
       13. The rotorcraft of  claim 1 , wherein the horizontal stabilizer control system is configured to receive information indicative of a need to enter an autorotation descent. 
     
     
       14. The rotorcraft of  claim 13 , further comprising:
 a plurality of wings; 
 wherein the horizontal stabilizer control system is configured to query a lookup table for a predetermined horizontal stabilizer position for minimizing lift generated by the plurality of wings of the rotorcraft during autorotation and maximizing airflow to a main rotor system of the rotorcraft. 
 
     
     
       15. The rotorcraft of  claim 14 , wherein the horizontal stabilizer control system is configured to control a horizontal stabilizer actuator to achieve the predetermined horizontal stabilizer position for minimizing lift generated by the wings and maximizing airflow to the main rotor system. 
     
     
       16. The rotorcraft of  claim 15 , wherein the horizontal stabilizer control system is configured to, after entering autorotation, receive information indicative of an actual or predicted deviation from the minimized wing lift position of the rotorcraft. 
     
     
       17. The rotorcraft of  claim 16 , wherein the horizontal stabilizer control system is configured to query a lookup table for a predetermined horizontal stabilizer position for minimizing lift generated by the wings during autorotation and maximizing airflow to the main rotor system. 
     
     
       18. The rotorcraft of  claim 17 , wherein the horizontal stabilizer control system is configured to control a horizontal stabilizer actuator to achieve the predetermined horizontal stabilizer position for minimizing lift generated by the wings and maximizing airflow to the main rotor system.